System and method for dimensioning a cdma network

ABSTRACT

The present invention a network based on code division multiple access techniques or CDMA for input parameters representing coverage requirements and/or capacity requirements and/or quality requirements able to provide at least per cell (η MAX ) given a plurality of services provided, comprising the steps of: determining a load factor per cell (η UL , η DL ) based on input parameters; characterised by the steps of: verifying whether the determined load factor (η UL , η DL ) corresponds to the maximum sustainable load (η MAX ) of a base terminal station and, if the determined load factor (η UL , η DL ) exceeds the maximum sustainable load factor (η MAX ); negotiating at the radio resource management (RRM) level at least one of the services provided in said network in such a way that the determined load factor (η UL , η DL ) becomes less than or equal to the maximum sustainable load (η MAX ) or is optimised taking into account the characteristics of the network.

TECHNICAL FIELD

The present invention relates to a system and method for thedimensioning or general (analytical) planning of a CDMA (Code DivisionMultiple Access) network.

In particular, the present invention relates to a system and method forthe analytical planing of a network for third generation UMTS (UniversalMobile Telecommunications System) mobile apparatuses which uses, as iswell known, a radio interface based on the Code Division Multiple Accesstechnique or CDMA.

BACKGROUND ART

The overall dimensioning (dimensioning) of a CDMA network consists, asis well known, of determining an estimate of the number andconfiguration of apparatuses constituting the mobile network able tomeet determined requirements.

In particular, analytical planning allows, starting from planningrequirements such as:

-   -   Coverage Requirements:        -   Planning area to be covered;        -   Geo-morphologic information about the planning area;        -   Propagation conditions;    -   Capacity requirements:        -   Available Frequency Spectrum;        -   Traffic Forecast per user;        -   Traffic Density over the area;    -   Quality Requirements:        -   Coverage Probability;        -   Block Probability;        -   User Throughput to be guaranteed;            the calculation with a certain degree of confidence, of            elements constituting the network, such as:    -   Number of Base terminal stations (BTS) or sites and        configuration thereof;    -   Equipment of the Base terminal stations in terms of:    -   maximum power required and average power per traffic channel;    -   required base band processing capacity;    -   Load per cell for geo-morphologically homogeneous area;    -   Percentage of use of the code tree;    -   Number of carriers used.

In the case of UMTS systems, which base their operation on a WCDMA (WideCDMA) radio interface characterised, as is well known, by the “SoftCapacity” property, the prior art, for instance as reported in the bookby H. Holma, A. Toskala, with the title “Radio Network Planning” onWCDMA for UMTS, Wiley & Sons Ltd. June 2000 recommends proceeding withthe overall planning on the basis of the assumption that:

-   -   dimensioning in terms of coverage (ability of the terminal to        communicate) must be verified by analysing the network in regard        to the radio link from the mobile terminal to the Base terminal        station (uplink); and    -   dimensioning in terms of capacity (the ability of the network to        provide services to the mobile terminal) must be verified by        analysing the network in regard to the radio link from the Base        terminal station to the mobile terminal (downlink).

In other words, a first limitation of the prior art consists of itsassumption that the effects of the uplink and of the downlink paths aredistinct and that therefore they can be evaluated in separate, thoughsequential, fashion.

Based on experience, it seems that such an assumption is not adequateand that a correct dimensioning of the network must be conductedintersecting or combining the analysis of the uplink path with that ofthe downlink path.

A second limitation of the prior art relating to the dimensioning of thenetwork by path, for instance for the uplink path, consists of the factthat it does not take into account that some services are negotiable, inparticular thanks to the intrinsic characteristics of CDMA networks.

Both the first and the second limitation, individually or jointly,entail, in general, that analytical planning in accordance with theprior art is particularly prone to yield imprecise results, even in theorder of 20-30% with respect to what can be obtained with more accuratemethods.

DISCLOSURE OF THE INVENTION

An aim of the present invention is to describe a new method for thegeneral planning of a CDMA network.

An aim of the present invention is also a system able to implement themethod according to the invention and a computer product which can beloaded into the memory of an electronic computer to carry out the methodaccording to the invention.

The aim is achieved by the system and method for dimensioning a CDMAnetwork as claimed.

According to a characteristic of the present invention, in dimensioningthe network the method takes into account, for each type of path, thefact that each service can be negotiated dynamically.

According to another characteristic of the present invention, given thejoint dimensioning, for the uplink and downlink path, verification stepsare provided that are able to request or to review the input parametersor to negotiate the services dynamically.

Naturally, the invention also relates to the computer product able to beloaded directly into the internal memory of an electronic computer tocarry out, when the product is executed on an electronic computer, themethod according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other characteristics of the present invention shall becomereadily clear from the following description of a preferred embodiment,provided by way of non limiting example with the aid of the accompanyingdrawings, in which:

FIG. 1 shows a system for the general planning (dimensioning) of anetwork for mobile apparatuses;

FIG. 2 shows a general block diagram of the method according to theinvention; and

FIG. 3A, FIG. 3B, FIG. 3C and FIG. 3D together show a single flow chartdescribing the method according to the invention and related to thedimensioning of a radio network according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to FIG. 1, a system for the general or analyticalplanning (known as “dimensioning”) of a mobile telecommunicationsnetwork comprises, for instance, a known computerised work station (WorkStation) 50 having a processing sub-system (base module) 51, a displaydevice (display) 52, a keyboard 55 and a pointing device (mouse) 56.

The Work Station 50, for example the model J5000 by Hewlett-Packard,with a 700 MHz CPUT, 128 Mbytes RAM, an 18 Gbyte hard disk drive and aWindows operating system, is able to process groups of programs, ormodules, stored, for instance, in the RAM, and to visualise the resultson the display 52.

In the described configuration, the system is able to allow, forinstance, the dimensioning of a network for mobile equipment orterminals on the basis of computerised modules stored in the memory ofthe Work Station 50 and able to implement the method according to theinvention as described below.

The method for the dimensioning of a mobile radio network based, forinstance, on a WCDMA (Wide-band CDMA) radio interface comprises aplurality of steps that can be grouped in to logic blocks (FIG. 2).

A first block (100) for preparing data for dimensioning the network.

A second block (200) for dimensioning the network considering, as shallbe described in detail hereafter, the radio path from mobile to Baseterminal station (uplink path) and/or the radio path from Base terminalstation to mobile (downlink path).

In particular, in the second block 200, planning is conducted both bymeans of specific dimensioning steps for the uplink path and specificdimensioning steps for the downlink path, and through multipleinteractions or feedback between the steps relating to the dimensioningof the uplink and of the downlink path.

Moreover, in the specific steps for dimensioning the uplink path, in amanner deemed to be novel, account is taken both of coverage and oftraffic aspects and, for the downlink path, account is taken both of thelimited number of orthogonal codes, typical for instance of UMTSnetworks, and of the limits of power per channel and total power of BaseTerminal Stations (or BTS).

The method according to the invention allows to improve dimensioningboth in regard to each path, considered individually, and for the twopaths, considered jointly, as shall be made readily apparent in thedescription that follows.

In the first block 100 are therefore provided all input parametersnecessary for the dimensioning of the network.

Said parameters, of a known type, correspond to those generally used bythe prior art to conduct the analytical planning of a mobile network andcan be considered as starting specifications or planning requirementsthat must be met by the dimensioning.

In particular, said parameters comprise, for instance, as previouslystated in the description:

-   -   Coverage requirements or parameters, such as:        -   dimension in Km² of the planning area;        -   percentages of the planning area distinguished by type of            area, for instance dense urban, urban, suburban, rural.    -   Capacity requirements or parameters, such as:        -   initial number of carriers;        -   number of usable carriers;        -   maximum load sustainable per cell or η_(MAX);        -   maximum percentage of use in terms of power of the BTS            stations to assure their correct operation;        -   maximum power per traffic channel associated to each service            on the downlink path;        -   expected percentage of soft handover connections;        -   number and type of services to be provided in the planning            area under consideration. Each type of service (service)            taken into consideration can be provided, as is well known,            by means of appropriate radio channel (Radio Access            Bearer—RAB) whereon the service is to be mapped            distinguishing among RABs of the following types:            -   CS (Circuit Switched): Voice AMR (Adaptive Multi Rate);            -   CS (Circuit Switched): for instance video-telephony;            -   PS (Packet Switched): for instance Web Browsing.

The configurations of the parameters that define the RABs (radiobearers) belonging to the three aforementioned families are set out, forexample, in the specification document 3GPPTS 34.108, published by theConsortium 3GPP.

-   -   Quality Requirements or Parameters.    -   Configuration Requirements or Parameters relating to possible        strategies for the configuration or development of the radio        network, such as:        -   Minimisation of the number of carriers used;        -   Minimisation of the number of sites used.

The latter parameters can, as will be readily apparent to a personversed in the art, influence the operations or functions carried out bythe block 200, albeit without modifying the characteristics of themethod according the invention.

FIGS. 3A, 3B, 3C and 3D show in greater detail the operations or stepscarried out in the second block 200.

In a first step (Step U1), the value of η_(max) is attributed, which isan input data time, to a reference variable called η_(start) and used,in accordance with the method described herein, to verify whether thedimensioning meets the starting specifications, as shall be described indetail hereafter.

In a second step (Step U2), the so-called “link budget” is calculated,as described in detail hereafter and, through it, the cell radius.

For instance, the calculation of the link budget and of the consequentcell radius is performed with reference to the uplink path, in foursub-steps:

I) Calculation of the EIRP (Equivalent Isotropic Radiated Power)EIRP_(Tx) of the terminal, using the known formula:EIRP _(Tx) =P _(tx) +G _(tx) −L _(tx)  [dBm]where:

-   P_(tx) is an input data item and corresponds to the maximum power of    the mobile terminal;-   G_(tx) is an input data item of the mobile terminal and corresponds    to antenna gain in transmission, defined as the maximum gain of the    antenna at the transmitter in the horizontal plane relative to an    isotropic radiator;-   L_(tx) is an input data item of the mobile terminal and represents    the connection losses of the transmitter;    -   L_(tx), in particular, takes into account all losses due to the        components positioned between the output of the transmitter and        the input of the antenna.

II) Calculation of the so-called sensitivity of the base terminalstation receiver (S_(rx)). In particular, S_(rx) is the power level ofthe minimum signal necessary at the input of the BTS receiver to meetrequirements in terms of E_(b)/N₀:$S_{rx} = {\frac{E_{b}}{N_{0}} + R_{dB} + S_{n} + F + {M_{imp}\quad\lbrack{dBm}\rbrack}}$where:

-   R_(dB) is the bit rate of the service expressed in dB;-   E_(b)/N₀ is the ratio between the energy per bit of information and    the spectral density of thermal noise+interference. The values of    E_(b)/N₀ used when calculating the link budget in uplink are    determined, in known fashion, by means of simulators of radio    reception and transmission chains, also known;-   S_(n) is the spectral density of thermal noise. S_(n)=k·T₀ with    k=1.38·10⁻²³ J/K Boltzmann constant and T₀=290K;-   F is the noise figure of the BTS receiver;-   M_(imp) is the so-called implementation margin; said parameter    M_(imp) takes into account any deviations from the ideal of the BTS    receiver and is linked to factors that depend on the construction of    the BTS itself.

III) Calculation of total path attenuation or “path loss” (A);

-   for each service said value (A) represents the maximum sustainable    “path loss”, i.e. the maximum loss that allows to obtain, starting    from the maximum power of the mobile, assumed to be at the cell    edge, the performance required from the BTS receiver:    A=EIRP _(Tx) −S _(rx) +G _(rx) −L _(rx) −M _(int) −M _(PC) +G    _(macro) −L _(ab) −M _(sh) −M _(PL)    where:-   G_(rx) is an input data item and it represents the reception antenna    gain of the BTS, defined as the maximum antenna gain at the receiver    in the horizontal plane with respect to an isotropic radiator;-   L_(rx) is an input data item and it represents the connection losses    of the BTS receiver. L_(rx) takes into account all losses due to the    components positioned between the output of the antenna and the    input of the BTS receiver;-   M_(int) is only initially an input data item that represents the    interference margin. In CDMA based cellular systems, the coverage    provided by a base station depends on the volume of traffic to be    handled: the greater the traffic, the lesser the coverage provided    by the cell. To take into account the influence of the load on the    calculation of the coverage, said interference margin is introduced,    which, as shall be seen and in accordance with the present    embodiment, is linked to the load factor η_(UL) of the cell through    the formula M_(int)=−10log₁₀(1−η_(UL)) and is updated in iterative    way according to the dimensioning congruence tests;-   M_(PC) is an input data item and it represents the power control    margin; said margin is inserted in the link budget computation to    allow a terminal located on the edge of the cell to increase    transmission power, to compensate for the variations of the received    signal due to fast fading. For this reason sometimes said margin is    also called “fast fading margin”;-   G_(macro) is an input data item and it represents macro diversity    gain; as is well known, in CDMA based cellular systems the terminal    can be simultaneously connected to two base terminal stations (the    so-called soft handover condition). This condition is also called    macro diversity. Thanks to said peculiar condition, it is possible    to lower the requirements on the E_(b)/N₀ ratio needed for the    individual connection. The macro diversity gain G_(macro) takes into    account the gain which the macro diversity allows to obtain against    shadowing;-   L_(ab) is an input data item and it represents the so-called    antenna/body loss. In particular, the term L_(ab) takes into account    the fact that part of the signal is absorbed by the human body. In    the case of high bit rate data services, said parameter is assumed    to be 0 dB, because it is supposed that the mobile terminal is    positioned at a sufficient distance from the body to consider    interaction to be nil;-   M_(sh) is an input data item and it represents the so-called    shadowing margin. The term M_(sh) takes into account the    fluctuations of the received signal due to the so-called    “shadowing”, and it is linked, as is well known, to an additional    parameter called coverage probability, which can be defined as a    function of the probability of an out of service condition, also    called “outage”, taken as the probability that the signal variation    due to shadowing exceeds the difference between maximum transmission    power and the level of signal required in reception. Since the    fluctuations due to shadowing have a log-normal distribution, to low    outage probabilities (high coverage probabilities) correspond high    shadowing margins. For instance, if a log normal distribution with a    standard deviation of 8 dB is considered, to a 10% probability of    outage corresponds a shadowing margin of 10.3 dB;-   M_(PL) is an input data item and it represents the so-called margin    of penetration. The term M_(PL) takes into account the losses due to    the presence of obstacles, typically buildings, between the    transmitter and the receiver.

IV) Calculation of the radius of each cell (R_(COP)) belonging togeo-morphologically homogeneous areas: after obtaining the value ofattenuation A [dB], the cell radius R_(COP) [km] is calculated in knownfashion with a path-loss formula that depends on the environment underconsideration.

For instance, in the case of multi-service scenarios, typical of thirdgeneration systems, such as the UMTS system as defined in the 3GPPstandard (Third Generation Partnership Project), the calculation of theradius R_(COP) is achieved by repeating the four sub-steps for eachservice and selecting the smallest amongst the radii thus obtained.

In a third step (Step U3), from the cell radius, dividing the planningarea considered by the area subtended by each cell it is possible toobtain the total number of cells and the traffic offered to each cell(Step U4).

In an additional step (Step U5A or U5B) one obtains, as a function ofthe type of service, for instance circuit switched (CS) or packetswitched (PS), the number of channels to be allocated on the uplinkpath. This calculation is carried out with the following mutuallyalternative steps:

-   -   5A] Erlang B Formula, in particular for CS (Circuit Switched)        services;    -   5B] Simplified wait models, in particular for PS (Packet        Switched) services.

In two successive steps (Step U6 e U7) the total load factor per cell ofthe uplink path (η_(UL)) is calculated; in particular, the followingformula is used:$\eta_{UL} = {\left( {1 + i} \right) \cdot {\sum\limits_{j = 1}^{N_{S}}\quad\frac{N_{j}}{1 + \frac{W}{\left( {E_{b}/N_{0}} \right)_{j} \cdot R_{j} \cdot \upsilon_{j}}}}}$in which the following parameters are known, i.e.:

-   i is the ratio between inter-cell interference and intra-cell    interference;-   N_(S) is the number of services offered in the cell;-   N_(j) is the number of users employing the j^(th) service;-   W is the chip rate;-   R_(j) is the bit rate associated to the j^(th) service;-   ν_(j) is the activity factor of the j^(th) service; and in which the    following parameter is used in a manner considered novel:    -   (E_(b)/N₀)_(j) is the requirement, in terms of the ratio (useful        signal power)/(total interference density), for the j^(th)        service.

The hypothesis that is generally adopted in the prior art, for thedownlink path as well, is the presence of an ideal power controlprocedure, such as to guarantee to the receiver the desired E_(b)/N₀ratio for each user; the value of the E_(b)/N₀ ratio is obtained, inthis hypothesis, from the results of the physical layer simulations.

One of the elements deemed distinctive of the present invention is thatof considering the effect of a real power control procedure, i.e. onethat is affected by delays, errors etc.

In order to consider this effect, taking into account that due to thenon ideal conditions of the power control procedure the values ofE_(b)/N₀ measured at the receiver follow a normal or Gaussiandistribution in decibels, and that to said distribution corresponds alog-normal distribution in linear, when the average value of E_(b)/N₀appears, the following expression was used:E[E _(b) /N ₀ ]=e ^(βm) ^(e) ·e ^((βσ) ^(e) ⁾ ² ^(/2)where:

-   -   m_(c) is the average value of the E_(b)/N₀ ratio expressed in        decibel;    -   σ_(c) is the variance of the E_(b)/N₀ ratio expressed in        decibel;    -   β=ln(10)/10.

This expression, deemed to be novel for the scope of the invention,allows to take into account power control procedures in real fashion, inparticular when evaluating the per service and total load factor η_(UL).Thanks to the fact that power control is taken into account in realfashion, it is possible to take into account, in the dimensioning of thenon ideal condition of the power control which is translated, forinstance for equal planning scenarios, into an increase of the number ofBTS required and of their equipment in terms, for example, of poweramplifiers.

Given the calculation of the load factor η_(UL), according to thepresent embodiment, the following step (Step U8) consists of verifyingwhether said value of η_(UL) corresponds to the initially set values(η_(START)) to carry out the dimensioning operation.

In particular, if the load factor ηUL thus determined coincides withη_(start) the method according to the invention provides, in a possibleembodiment, for the start of a set of steps for the dimensioning of thedownlink path starting from Step D1.

This embodiment also seems novel with respect to the prior art.

If, instead, η_(UL) is smaller than η_(start) then the steps U2-U7 arerepeated assigning a smaller value to η_(start) (Step U15), untilequality is verified (Step U8, outcome η_(UL)=η_(start)) in order toproceed, subsequently, to Step D1 as indicated above.

If η_(UL) is greater than η_(start) the method, according to anadditional peculiar characteristic of the present invention, verifieswhether the RAB can be renegotiated (Step U9) and, if it is, it proceedsto “renegotiate” at least one of the services or a type of service (StepU14).

This methodology is possible, as will be readily apparent to a personversed in the art, because CDMA networks, for instance UMTS networks areof the multi-service type, i.e. networks in which a plurality ofdifferent services is provided.

In the case of RAB of the PS (Packet Switched) type, according to thepresent embodiment, a maximum Bit Rate and a minimum Bit Rate are set,compatible with the characteristics of the quality of the service to benegotiated.

Said bit rate may vary dynamically according to the contingentconditions of operation of the network, for instance the radio network(e.g. variation of the system load, variation of the radio interfaceload).

The dynamic variations of the bit rate of each renegotiable service aremanaged, as is well known, at the RRM level (Radio ResourcesManagement), by means of functionalities, for instance, of the “packetscheduling” and “congestion control” type.

The method according to the invention takes into account, at thedimensioning level, of the impact that “packet scheduling” and“congestion control” functionalities have on the network.

In particular, the “packet scheduling” functionality is simulated byvarying the bit rate between maximum and minimum values as indicatedwhen, based on the “congestion control” functionality, the situation inwhich η_(UL) exceeds η_(start) is identified (Step U8,η_(UL)>η_(start)).

Moreover, by means of an additional RRM level functionality, called“admission control” in the specifications, the method according to theinvention provides for blocking parameters able to block the traffic ofeach cell both on the uplink and on the downlink path.

In the case of voice CS RAB, for instance in the case of UMTS networks,the method according to the invention provides for the so-called AMR(Adaptive Multi Rate) coding whereby the service is renegotiatedsimulating voice coding at different bit rates, for instance between4.75 Kbps and 12.2 Kbps.

According to said coding, under particular operating conditions of theradio network, for instance with high load or in poor propagationconditions, the voice service is mapped on a RAB-voice-AMR with lowerbit rate that requires less of an impact from the point of view of theradio interface.

The method according to the present invention takes into account theimpact of the AMR functionality on the network.

Therefore, according to the present embodiment, the method provides forrenegotiating individual services or individual types of service, forinstance by changing the bit rate of a service, for example decreasingand increasing the required value of E_(b)/N₀.

Thanks to this approach, once the parameters that define the RAB onwhich the service is provided are modified, the method allows to startfrom the initial step U1 in order to recalculate η_(UL).

As shall be seen hereafter, the possibility of renegotiating the bearerof a service is also used to dimension the downlink path.

If instead it is not possible to renegotiate the radio bearer of anyallocated service (Step U9, negative outcome), depending on thedimensioning criterion selected in the first block 100 of definition ofthe parameters for the analytical planning, if possible, the number ofallocated carriers is, for example, increased, equally distributing thetraffic offered for each carrier (Step U11), or, alternatively, the cellradius is reduced (Step U12) and the steps U3-U7 are repeated in such away as to vary η_(UL) until reaching the equality η_(UL)=η_(start) (StepU8).

As will be readily apparent to a person versed in the art, the firstchoice corresponds to the strategy of minimising the number of sitesused, whilst the second one corresponds to the strategy of minimisingthe carriers used.

Once the equality η_(UL)=η_(start) is determined, the dimensioning ofthe downlink path is accomplished, in a possible embodiment.

The dimensioning of the downlink path has two objectives:

-   -   to test whether the downlink codes tree is able to host all the        channels of the services required; in this way, in a manner        deemed novel with respect to the prior art, an additional RRM        functionality, called “code management” is taken into account;    -   to test whether limits on transmission power are obeyed, both        for the individual service and for total power transmitted by        the BTS (“power management” verification); the verification of        the BTS power, which generally has a considerable impact on        dimensioning, is deemed novel with respect to the prior art.        This verification allows to take into account the “admission        control” RRM functionality for the downlink path.

Since these are test operations, the method provides, on each occasionwhen the outcome of the test is unsatisfactory, for repeating the stepsfor calculating the uplink path, as will be described in detailhereafter.

Starting from the number of cells obtained from the dimensioning for theuplink path, in the downlink path the following parameters are computed:

-   -   in a first Step D1, the traffic offered per cell belonging to a        geo-morphologically homogeneous area, dividing input traffic for        each service by the number of cells obtained from the        dimensioning of the uplink path;    -   in a second Step D2A or D2B, the number of channels that must be        allocated, also taking into account the percentage of channels        in soft handover; this calculation is performed, alternatively,        using:        -   the Erlang B formula for CS services (Step D2A);        -   simplified wait models for PS services (Step D2B);    -   in a further Step D3, from the number of channels obtained it is        possible to calculate the occupation on the code tree for each        cell; in particular, it is possible to verify whether the codes        relating to the requested services can be hosted on the code        tree associated to each BTS.

This verification entails a series of alternatives.

If it is not possible to host all codes provided in downlink (Step D3,negative outcome) and if at least one service can be renegotiated (StepD4, positive outcome), the method returns to Step U14 so that adifferent RAB is renegotiated for that service.

In this way the “packet scheduling” and “congestion control”functionality is taken into account on the downlink path.

If there is no renegotiable service (Step D4, negative outcome), thentwo alternatives are possible, depending on the choices made in theblock 100 of initial choices for the uplink and downlink path in regardto possible network development strategies:

-   -   Reducing the radius of the cell until obtaining a number of        downlink channels that can be hosted by a single code tree (Step        D5 followed by verification Step 3 with positive outcome);    -   Allocating, if available, an additional carrier (Step D6). In        this case the traffic is subdivided between the carriers and the        method starts back from Step U1 to recalculate η_(UL).

If the first possibility is chosen (Step D5 and Step D3, positiveoutcome), or if the code occupation test had a positive outcome (StepD3, positive outcome), the load factor is calculated for each servicefor each individual cell on the downlink path η_(DL), based on thefollowing known formula (Steps D8A and D8B):$\eta_{DL} = {\sum\limits_{i = 1}^{I}\quad{\frac{\left( {E_{b}/N_{0}} \right)_{i} \cdot R_{i} \cdot \upsilon_{i}}{W} \cdot \left\lbrack {\left( {1 - \alpha_{i}} \right) + i_{i}} \right\rbrack}}$where:

-   I is the number of users in the cell;-   i_(i) is the ratio between the inter-cell interference and the    intra-cell interference received by the ith terminal. In the    algorithm, an average value for all users is employed for this    parameter;-   W is the chip rate;-   R_(i) is the bit rate associated with the i^(th) terminal;-   ν_(i) is the activity factor of the i^(th) terminal;-   α_(i) is the orthogonality factor of the i^(th) terminal which    depends on the conditions of propagation (α_(i)=1 in case of perfect    orthogonality between the signals in downlink). In the algorithm, an    average value for all users is employed for this parameter;-   (E_(b)/N₀)_(i) is the requirements, in terms of useful signal    power/total interference density ratio, for the i^(th) terminal.

After determining the values of η_(DL) it is possible to use thefollowing known formula to calculate the transmission power forindividual services and total transmission power (Steps D9A and D9B)using the following formula:$P = \quad\frac{\frac{P_{N}{\sum\limits_{i = 1}^{I}{\left( {E_{b}/N_{0}} \right)_{i} \cdot R_{i} \cdot \upsilon_{i}}}}{W} \cdot L_{m,i}}{1 - \eta_{DL}}$where:

-   P_(N) is thermal noise power;-   L_(m,i) is the attenuation undergone by the signal in the downlink    path connecting the base station to the terminal.

After calculating the power, the method according to the presentinvention proceeds to compare maximum power sustainable per trafficchannel for a service (Power Management test) with the maximum powercalculated for the same service (Step D10A);

If the maximum calculated power per channel of at least one serviceexceeds maximum power (Step D10A, positive outcome) and the service canbe renegotiated (Step D10B, positive outcome) the method returns to stepU14 and the RAB is renegotiated.

The effect of renegotiation is dual: increase in (E_(b)/N₀)_(i) anddecrease in bit rate R_(i) The preponderant effect is the latter, whichentails the decrease of the power required in transmission andconsequent variation of η_(UL).

If it is not possible to renegotiate a different RAB (Step D10B,negative outcome), according to the present method it is possible,taking into account the dimensioning criteria chosen in the first block100 and until the limit on power is obeyed, to complete the dimensioningprocess, in alternative fashion:

-   -   by increasing, if possible, the number of carriers used (Step        D6) and starting anew from Step U1;    -   by decreasing cell radius (Step D18) and recycling on Step D10A;    -   by increasing BTS power until the power limit is obeyed.

If no service exceeds the power limits (Step D10A, negative outcome), inaccordance with the present embodiment a last test on total transmittedpower is conducted (Step D11).

If total power P determined is lower than the maximum power available,the method is completed and the determined values correspond to thedimensioning of the network (Step D11, positive outcome).

In the opposite case (Step D11, negative outcome) and if the servicesare renegotiable (Step D12, positive outcome) the RAB are renegotiatedfor the services that are still renegotiable (Step U14) and thecalculation process is repeated starting from Step U1.

If there are no renegotiable services, taking into account thedimensioning criterion selected in the first block 100 and until thelimit on power is obeyed, ending the dimensioning process in alternativefashion through the following choices:

-   -   by increasing, if possible, the number of carriers (Step D6) and        starting again the calculation process from Step U1;    -   by decreasing cell radius until the limit on total maximum        transmission power is obeyed (Step D18) and starting again from        Step U3;    -   by increasing the power of the BTS until the power limit is        obeyed.

The method described herein, and the corresponding system configured toimplement the method, therefore allow, in a manner deemed innovative,both to:

-   -   dimension, in joint fashion, the uplink and the downlink path        for a determined territory; and to    -   negotiate in dynamic fashion the services, both for the uplink        and for the downlink path, taking into account RRM        functionalities such as:        -   Power control;        -   Packet Scheduling;        -   Congestion control;        -   Admission control;        -   AMR voice coding;        -   Code management; and        -   Power management.

Thanks to these characteristics, the method according to the presentinvention allows to optimise the values of maximum sustainable load percell and, hence, to achieve a greater accuracy in the analyticalplanning of the number of sites, number of BTS and associated equipment.

In particular, the results verified experimentally differ from thoseachievable with the prior art by percentages in the order of 20-30%.

Obvious modifications or variations can be made to the descriptionprovided above, in dimensions, shapes, materials, components, circuitelements, connections and contacts, as well as in the details of thecircuitry and of the construction illustrated herein and in theoperating method without thereby departing from the spirit of theinvention as set out in the claims that follows.

1. Method for dimensioning a network based on Code Division MultipleAccess techniques or CDMA for input parameters that are representativeof coverage requirements and/or capacity requirements and/or qualityrequirements able to provide at least a value of maximum sustainableload per cell (η_(MAX)) given a plurality of services provided,comprising the steps of: determining a load factor per cell (η_(UL),η_(DL)) on the basis of the input parameters; characterised by the stepsof: verifying whether the determined load factor (η_(UL), η_(DL))corresponds to the maximum load sustainable (η_(MAX)) by a base terminalstation or BTS and, if the determined load factor (η_(UL), η_(DL))exceeds the maximum sustainable load negotiating at the Radio ResourceManagement (RRM) level at least one of the services provided in saidnetwork in such a way that the determined load factor (η_(UL), η_(DL))becomes smaller than or equal to the maximum sustainable load (η_(MAX))or is optimised taking into account the characteristics of the network.2. Method as claimed in claim 1, characterised in that the load factoris determined taking into account real “power control” procedures, byattributing to the ratio between useful signal power and totalinterference density of the BTS a normal or Gaussian distribution indecibels.
 3. Method as claimed in claim 1 or 2, characterised in thatthe step of determining the load factor is carried out for the uplinkradio path.
 4. Method as claimed in claim 3, characterised in that thestep of negotiating at least one of the services provided comprises thestep of negotiating one among the functionalities of packet scheduling;congestion control; and admission control.
 5. Method as claimed inclaims 1 or 2, characterised in that the step of determining the loadfactor is carried out for the downlink radio path
 6. Method as claimedin claim 5, characterised in that the step of negotiating at least oneof the services provided comprises the step of negotiating one among thefunctionalities of code management; power management; packet scheduling;congestion control; and admission control.
 7. Method for dimensioning anetwork based on Code Division Multiple Access techniques or CDMA forinput parameters that are representative of coverage requirements and/orcapacity requirements and/or quality requirements able to provide atleast a value of maximum sustainable load per cell (η_(MAX)) and amaximum number of radio channels associated with corresponding codesprovided for a plurality of services provided, comprising the steps of:determining by means of “link budget” a load factor per cell for theuplink radio path (η_(UL)); and characterised by the steps of: verifyingwhether the determined load factor (η_(UL)) corresponds to the maximumload sustainable (η_(MAX)) by a base terminal station or BTS, and if theoutcome of the verification is positive; determining by means of “polecapacity” the number of radio channels and corresponding associatedcodes for the downlink radio path; verifying whether the codes providescan be hosted in the associated codes and if the number of associatedcodes exceeds the codes provided for at least one service; negotiatingat the Radio Resource Management (RRM) level at least one of theservices provided in said network in such a way as to update the maximumsustainable load (η_(MAX)).
 8. Method as claimed in claim 7,characterised by the further steps of determining for each service aload factor per cell (η_(DL)) and corresponding values of power perchannel for the downlink radio path; verifying whether the power perchannel of at least one service exceeds power limits prescribed for saidservice and, if the power per channel of at least one service exceedsthe prescribed power limits; negotiating said service at the RadioResource Management (RRM) level in such a way as to update the maximumsustainable load (η_(max)).
 9. System for dimensioning a radio networkbased on Code Division Multiple Access or CDMA techniques, comprising acomputerised work station (50) programmed for implementing the method asclaimed in any of the previous claims.
 10. Computer product able to beloaded directly into the internal memory of a computerised work station(50) and comprising portions of software code to carry out, when theproduct is executed on the work station, the method as claimed in any ofthe claims from 1 through 8.